[PATCH v10 12/12] fprobe: Add a selftest for fprobe

Masami Hiramatsu
2022-03-08T11:11:03Z

Add a KUnit based selftest for fprobe interface.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v9:
- Rename fprobe_target* to fprobe_selftest_target*.
- Find the correct expected ip by ftrace_location_range().
- Since the ftrace_location_range() is not exposed to module, make
this test only for embedded.
- Add entry only test.
- Reset the fprobe structure before reuse it.
---
lib/Kconfig.debug | 12 ++++
lib/Makefile | 2 +
lib/test_fprobe.c | 174 +++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 188 insertions(+)
create mode 100644 lib/test_fprobe.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 14b89aa37c5c..ffc469a12afc 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2100,6 +2100,18 @@ config KPROBES_SANITY_TEST

Say N if you are unsure.

+config FPROBE_SANITY_TEST
+ bool "Self test for fprobe"
+ depends on DEBUG_KERNEL
+ depends on FPROBE
+ depends on KUNIT
+ help
+ This option will enable testing the fprobe when the system boot.
+ A series of tests are made to verify that the fprobe is functioning
+ properly.
+
+ Say N if you are unsure.
+
config BACKTRACE_SELF_TEST
tristate "Self test for the backtrace code"
depends on DEBUG_KERNEL
diff --git a/lib/Makefile b/lib/Makefile
index 300f569c626b..154008764b16 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -103,6 +103,8 @@ obj-$(CONFIG_TEST_HMM) += test_hmm.o
obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o
obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
obj-$(CONFIG_TEST_REF_TRACKER) += test_ref_tracker.o
+CFLAGS_test_fprobe.o += $(CC_FLAGS_FTRACE)
+obj-$(CONFIG_FPROBE_SANITY_TEST) += test_fprobe.o
#
# CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns
# off the generation of FPU/SSE* instructions for kernel proper but FPU_FLAGS
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
new file mode 100644
index 000000000000..ed70637a2ffa
--- /dev/null
+++ b/lib/test_fprobe.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * test_fprobe.c - simple sanity test for fprobe
+ */
+
+#include <linux/kernel.h>
+#include <linux/fprobe.h>
+#include <linux/random.h>
+#include <kunit/test.h>
+
+#define div_factor 3
+
+static struct kunit *current_test;
+
+static u32 rand1, entry_val, exit_val;
+
+/* Use indirect calls to avoid inlining the target functions */
+static u32 (*target)(u32 value);
+static u32 (*target2)(u32 value);
+static unsigned long target_ip;
+static unsigned long target2_ip;
+
+static noinline u32 fprobe_selftest_target(u32 value)
+{
+ return (value / div_factor);
+}
+
+static noinline u32 fprobe_selftest_target2(u32 value)
+{
+ return (value / div_factor) + 1;
+}
+
+static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
+{
+ KUNIT_EXPECT_FALSE(current_test, preemptible());
+ /* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
+ if (ip != target_ip)
+ KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
+ entry_val = (rand1 / div_factor);
+}
+
+static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
+{
+ unsigned long ret = regs_return_value(regs);
+
+ KUNIT_EXPECT_FALSE(current_test, preemptible());
+ if (ip != target_ip) {
+ KUNIT_EXPECT_EQ(current_test, ip, target2_ip);
+ KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor) + 1);
+ } else
+ KUNIT_EXPECT_EQ(current_test, ret, (rand1 / div_factor));
+ KUNIT_EXPECT_EQ(current_test, entry_val, (rand1 / div_factor));
+ exit_val = entry_val + div_factor;
+}
+
+/* Test entry only (no rethook) */
+static void test_fprobe_entry(struct kunit *test)
+{
+ struct fprobe fp_entry = {
+ .entry_handler = fp_entry_handler,
+ };
+
+ current_test = test;
+
+ /* Before register, unregister should be failed. */
+ KUNIT_EXPECT_NE(test, 0, unregister_fprobe(&fp_entry));
+ KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp_entry, "fprobe_selftest_target*", NULL));
+
+ entry_val = 0;
+ exit_val = 0;
+ target(rand1);
+ KUNIT_EXPECT_NE(test, 0, entry_val);
+ KUNIT_EXPECT_EQ(test, 0, exit_val);
+
+ entry_val = 0;
+ exit_val = 0;
+ target2(rand1);
+ KUNIT_EXPECT_NE(test, 0, entry_val);
+ KUNIT_EXPECT_EQ(test, 0, exit_val);
+
+ KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp_entry));
+}
+
+static void test_fprobe(struct kunit *test)
+{
+ struct fprobe fp = {
+ .entry_handler = fp_entry_handler,
+ .exit_handler = fp_exit_handler,
+ };
+
+ current_test = test;
+ KUNIT_EXPECT_EQ(test, 0, register_fprobe(&fp, "fprobe_selftest_target*", NULL));
+
+ entry_val = 0;
+ exit_val = 0;
+ target(rand1);
+ KUNIT_EXPECT_NE(test, 0, entry_val);
+ KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+ entry_val = 0;
+ exit_val = 0;
+ target2(rand1);
+ KUNIT_EXPECT_NE(test, 0, entry_val);
+ KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+ KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
+}
+
+static void test_fprobe_syms(struct kunit *test)
+{
+ static const char *syms[] = {"fprobe_selftest_target", "fprobe_selftest_target2"};
+ struct fprobe fp = {
+ .entry_handler = fp_entry_handler,
+ .exit_handler = fp_exit_handler,
+ };
+
+ current_test = test;
+ KUNIT_EXPECT_EQ(test, 0, register_fprobe_syms(&fp, syms, 2));
+
+ entry_val = 0;
+ exit_val = 0;
+ target(rand1);
+ KUNIT_EXPECT_NE(test, 0, entry_val);
+ KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+ entry_val = 0;
+ exit_val = 0;
+ target2(rand1);
+ KUNIT_EXPECT_NE(test, 0, entry_val);
+ KUNIT_EXPECT_EQ(test, entry_val + div_factor, exit_val);
+
+ KUNIT_EXPECT_EQ(test, 0, unregister_fprobe(&fp));
+}
+
+static unsigned long get_ftrace_location(void *func)
+{
+ unsigned long size, addr = (unsigned long)func;
+
+ if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
+ return 0;
+
+ return ftrace_location_range(addr, addr + size - 1);
+}
+
+static int fprobe_test_init(struct kunit *test)
+{
+ do {
+ rand1 = prandom_u32();
+ } while (rand1 <= div_factor);
+
+ target = fprobe_selftest_target;
+ target2 = fprobe_selftest_target2;
+ target_ip = get_ftrace_location(target);
+ target2_ip = get_ftrace_location(target2);
+
+ return 0;
+}
+
+static struct kunit_case fprobe_testcases[] = {
+ KUNIT_CASE(test_fprobe_entry),
+ KUNIT_CASE(test_fprobe),
+ KUNIT_CASE(test_fprobe_syms),
+ {}
+};
+
+static struct kunit_suite fprobe_test_suite = {
+ .name = "fprobe_test",
+ .init = fprobe_test_init,
+ .test_cases = fprobe_testcases,
+};
+
+kunit_test_suites(&fprobe_test_suite);
+
+MODULE_LICENSE("GPL");